Prostaglandin analogs for structure-activity studies are being synthesized in order to test the "hairpin conformation" model for bioactivity. These include analogs in which the hairpin conformation is maintained by hydrophobic interactions, by covalent bonds in macrocyclic rings, or the steric interactions. The conformational preferences of the analogs prepared in connection with the structure-activity studies, natural prostaglandins, and diastereomers of the natural substances are being investigated by a combination of nmr shift and relaxation data and CD spectroscopy in order to determine physico-chemical correlates of biological potency and to define the precise conformational requirements at various prostaglandin receptors. Polymer-bound prostaglandins are being evaluated as agonists, clinical assay reagents, and as affinity-chromatographic media for the isolation and purification of prostaglandin metabolizing enzymes.